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Dynamic Gain And Channel Equalizers - Patent 6888983

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Dynamic Gain And Channel Equalizers - Patent 6888983 Powered By Docstoc
					
				
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Description: 1. Field of the InventionThe present invention relates generally to beam refraction systems, and more particularly to dynamic gain equalizers, spectrum analyzers and dynamic channel equalizers that are used in a dynamic compensation system that provides feedback acrossthe entire spectrum.2. Description of Related ArtWavelength division multiplexing (WDM) provides a technique for increasing a transmission capacity by a single optical fiber. In a system adopting WDM, a plurality of optical carriers with different wavelengths are used. The plural opticalcarriers are individually modulated to obtain a plurality of optical signals. These are wavelength division multiplexed by an optical multiplexer to obtain WDM signal light which is output to an optical fiber transmission line. On the receiving side,the WDM signal light received is separated into individual optical signals by an optical demultiplexer, and transmitted data is reproduced according to each optical signal. Accordingly, by applying WDM, the transmission capacity in a single opticalfiber can be increased according to the number of WDM channels.In the case of incorporating an optical amplifier into a system adopting WDM, a transmission distance is limited by the wavelength characteristic of gain which is represented by a gain tilt or gain deviation. For example, in an EDFA, it is knownthat a gain tilt is produced at wavelengths in the vicinity of 1.55 mu m, and this gain tilt varies with total input power of signal light and pump light power to the EDFA.A gain equalization method is known that measures against the wavelength characteristic of gain of an optical amplifier. A plurality of optical signals with different wavelengths are output from optical senders and are multiplexed in an opticalmultiplexer to obtain WDM signal light. The WDM signal light is then output to an optical transmission line which is configured by inserting a plurality of optical amplifiers, that compensate for losses, and at